The heat capacity Cp is a thermo-physical property. The heat capacity of a medium as well as the heat capacities of different parts of a setup has to be known for scale-up processes, reactor design as well as for safety assessments. The heat capacity of a medium or of a sample, e.g. a fluid, is often determined with calorimetric methods, which comprise the application of a specific temperature profile, such as a temperature ramp, to a medium inside a reactor. The temperature profile is usually generated and controlled by a temperature-controlling system, which interacts with the reactor.
Calorimetric experiments are easy to conduct but harbor several drawbacks concerning the accuracy of the obtained data. The accuracy is influenced by the calibration procedure, the instrumental noise and heat losses, e.g. through the reactor and its temperature-controlling system. Additionally, such experiments can be very time consuming. The accuracy of the determination of the heat capacity Cp can be enhanced by utilizing large temperature differences, but as the heat capacity Cp depends on the temperature small temperature differences would be sufficient to obtain accurate data.
A common, but time consuming technique for the determination of the heat capacity Cp is the differential scanning calorimetry (DSC), where a temperature difference between a sample and a reference is measured as a function of time, while a temperature profile is applied to the sample and the reference. This technique requires the individual preparation of each sample. Additionally, inhomogenities can occur in the sample, as this is placed in a small cup without stirring. These inhomogenities can have a negative impact on the experimental results.
A comparable technique for the determination of an absolute value of the heat capacity on a bigger scale has been disclosed in U.S. Pat. No. 6,071,008 A, where a stainless steel tube is arranged in a thermal bath which temperature can be controlled electrically.
European published application EP 0 647 839 A1 discloses the determination of the global heat transfer coefficient in a chemical reactor while a forced temperature oscillation is applied. The reactor is a classic double walled reactor with a thermostat comprising a heat carrier, such as a temperature controlled jacket or hollow coil, which is in contact with the reactor, filled with a heat-transfer medium and interacting with a heating/cooling unit such as a heat exchanger. This technique is also prone to inhomogenities and in particular to local inhomogenities in the sample, which have a negative impact on the results. Especially, the precise and timely control of the thermostat presents a difficulty, as some of the common heat carriers show a delayed reaction on temperature changes. The heat flow through the reactor is generally determined via the temperature difference between the temperature inside the reactor and the temperature of thermostat in particular of the heat carrier.
Therefore, the object of this invention is the development of a method for a fast and accurate determination of the heat capacity and the overall heat coefficient independent from each other, which overcomes the drawbacks of the prior art, and of a calorimeter for performing said method.